Background and Design:Enumeration of malignant cells in Sézary syndrome often relies on the identification of the Sézary cell nucleus. This morphologic method is, however, nonspecific and unreliable in the enumeration of the proportion of malignant lymphocytes in peripheral blood of patients with Sézary syndrome. Malignant lymphocytes of patients with mycosis fungoides and Sézary syndrome are often characterized by multiple chromosome aberrations. Herein, we demonstrate that fluorescent in situ hybridization can visualize and accurately enumerate malignant aneuploid mononuclear cells in a patient with Sézary syndrome.

Results:Fluorescent in situ hybridization demonstrated that 90% of the mononuclear cells in the patient with Sézary syndrome showed numerical aberrations for both chromosome 7 and X, a figure confirmed by flow cytometry.

Conclusion:Fluorescent in situ hybridization may be a valuable tool to visualize and enumerate aneuploid tumor cells in patients with cutaneous T-cell lymphoma.(Arch Dermatol. 1993;129:1141-1145)